Ceriatone clone Bassman 5F6A hum problem?

[vincenzo]

Hi, I'm Vincenzo from Italy. I hope to find here the answer to my problem.
I've buid a 5F6A Bassman Ceriatone layout. The amp works fine but I see that turn the volume pot (normal or bright) after halfway I hear a hum, or noise that increase with increasing volume.
This also happens if I do not connect the guitar.
I do not know if it is normal in a 5F6A or is there something wrong.
For example, I noticed that the Vox AC30 (factory built) a friend of mine has the same behavior. Silent until the volume control is halfway. Next, hum!
Any idea?

[tubenit]

Not normal.   Probably a ground problem or bad solder joint.  Could be an issue with the input jack wiring or ground?

With respect, Tubenit

[stratele52]

Hi Vicenzo ,

Building a amp is not only putting parts together like plastic cars or airplane kits. The way you put the wiring , the lenght must be in the right way . If not , you may have some hum.

Do you have any center tap to ground for the tube's heater ?

We need some good photos of your amp and wiring .

Any link to see this Ceriatone kit , layout ?

By the way I go 3 time in Italy ( from Canada) and I love your country and people.

[sluckey]

The amp works fine but I see that turn the volume pot (normal or bright) after halfway I hear a hum, or noise that increase with increasing volume.

How much noise? You can barely hear it? It's slightly objectionable in the bedroom but would not be noticeable in a club? It distracts from the guitar sound? It drowns out the guitar signal? It hurts your ears?

It's normal to have some hum or background noise/hiss when you turn the volume up. I can hear all of my amps when turned up in my bedroom. It would not be normal if the hum/noise is objectionable or makes the amp unusable. If your amp produces a level of hum/noise that is comparable with a factory built Vox AC30 I'd tend to say that's normal.

[stratele52]

You are right sluckey ,

Normal or not ?
Vincenzo write his friend VOX AC 30 do same noise . I fix noise on few Vox made in England , They where better after some work .

This Ceriatone 5F6 is a Basman 5F6 .Most Fender amp are "quiet" .

Just I have to say to Vicenzo is check is wiring layaout like photos on Ceriatone;

www.ceriatone.com/productSubPages/AC5F6ABassman/AC5F6ACompleteAmpHead.htm

[vincenzo]

Let's say that with the volume up and not playing a guitar that is a bit annoying.
In a club almost certainly would not be evident.
It not distract from the guitar sound.
It not drowns out the guitar signal.
It not hutrs my ears.

[vincenzo]

I've alrady done like Ceriatone but I had hum. Now I change the wiring

[stratele52]

Vincenzo, sorry but your wiring is poor . Almost all the wire are too long . Also they must follow the bottom of the chassis and wire must cross another in 90 degree , never side by side etc .

 Sure , with this kind of wiring you 'll have some noise.

 Look a the photos on Ceriatone link I post . And do same

[eleventeen]

I vote for the heater center tap as the problem. I don't see one (or....the two 100 ohm resistors to ground) .....but that doesn't mean they are not there.

[stratele52]

Are shorting input jacks are working , go to ground ?

[Guitarzan]

stratele52 is absolutely correct about wiring. The input side should have all of the wires be only as long as they need to be to make the connection with only the bare minimum of extra length for wire management purposes. The heater wires sould be carefully twisted and managed from one tube socket to the next. Much like the way the twist in a CAT5 cable helps to cancel out the noise from the other wires, your twist in those heater wires will make a difference as well. I've built so many 5F1 clones that I've lost count and not one of them makes any discernable noise with no instrument plugged in and volume at 12. If you get your head close to the amp you hear a faint hiss. That's it. I've also done several 5E3s and while I believe the push/pull curcuit is probably more prone to picking up some stray noise, my 5E3s are also as close to dead silent as you can get. Here's an example of what one of mine looks like when it's done.  I also make sure and shield the back panel with that metal tape the HVAC guys use on ductwork joints. That will not only keep any stray RF from getting in but it makes that whole back panel a great heat sink as well.
I hope that helps.
-d {8^)

[vincenzo]

I vote for the heater center tap as the problem. I don't see one (or....the two 100 ohm resistors to ground) .....but that doesn't mean they are not there.

Where should these two 100R resistors?

[stratele52]

Very nice job guitazan , congrat.

[Ed_Chambley]

Recently I have had 2 amps that would get noise from the volume pot.  From about half way to 3/4 and then quite.  The treble pot has some influence on it as well.  Both amps had artificial center taps and the resistors had drifted very badly.  In both cases they looked ok, so I did not check them first.  I made a post and Sluckey and Willabe explained elevated center taps.  So while I was replacing the resistors I referenced the artificial center taps to about 80vdc.

Both were Push Pull Princeton's.  It worked so well I ended up doing it to a few of my amps.  Humdingers work very well too.

I agree to clean up the wiring, the above are just suggestions if you want to get rid of as much floor noise as possible.

[stratele52]

I vote for the heater center tap as the problem. I don't see one (or....the two 100 ohm resistors to ground) .....but that doesn't mean they are not there.

Where should these two 100R resistors?

2 X 100 ohms OR a ground heater wire , green / yellow wire from the power transformer .

[vincenzo]

Are shorting input jacks are working , go to ground ?

I do not understand what you mean.

[vincenzo]

I vote for the heater center tap as the problem. I don't see one (or....the two 100 ohm resistors to ground) .....but that doesn't mean they are not there.

Where should these two 100R resistors?

2 X 100 ohms OR a ground heater wire , green / yellow wire from the power transformer .

Ah, ok!! My Hammond trasformer have a wire ground green/yellow.

Still do not understand. I've already shortened the wires. Before they were longer. I could not make it shorter because I have trouble doing it inside the chassis

I also replaced the heater wires with solid wire and twisted. Even these will seem long?
Can you tell me which wires should I shorten?

[eleventeen]

If you have EITHER a filament center tap (yellow-green, as you say) connected to ground OR the 2 x 100 ohm resistors, you should be fine.

The shielding on the back panel is potentially a big deal as far as noise.

Folks here have many, many 5E3 amps, I have not. Pay attention to their suggestions!

[Ed_Chambley]

Looking at all the photos, it looks as if most of the wires could be shorter, but don't get hung up on that just yet.  You can check your wiring by taking a wooden stick (chopstick works good and so does a pencil).  Run the amp and use the stick to move the wires around and see if your noise changes.  In these places you may need to rework the wiring.

The main thing right now is to insure you have a Center Tap for the Filaments/heaters.  If not, correct this first and then if you still have objectionable noise, start checking your wires by moving them with the stick.  If you find one and need to rework it.  Shut down, bleed off your caps and reroute the problem area.

You can clip on a jumper wire to pin 1 of your first tube for about 30 seconds and it will drain your caps.  Then the amp will be safe to work on provided you have it unplugged from the wall.

[Willabe]

I don't trust using a pencil. The graphite that's used instead of lead is extremely conductive.

OTOH, PRR has posted a number of times saying how to use a pencil to find the spot where an amp was unstable?

Graphite makes great fishing poles and every now and then a guy gets zapped by lighting as he's got the pole up (lighting rod) in the air casting. I've seen a good number of pictures of guys gym shoes with the soles blown off of them from the lighting strike trying to go out their feet and to ground through the boats hull to the water.


           Brad    

[Guitarzan]

I think Ed has put you on a good track to finding a solution. On a Fender vibrochamp I worked over the chopstick thing was perfect for finding areas in need of working over. I would do that for sure. Someone else said don't get too hung up on shortening wires and I agree. I would resolder anything that doesn't actually need it. you're just asking for trouble doing that. The methodical approach is the way to go. Just consider the wire management for the next build.
-d {8^)

[vincenzo]

So, I confirm that the transformer has the ground wire for the heaters and it is anchored to the chassis.
Tomorrow I will do the test with the piece of wood to beat all the wires, also I will try to shorten the wires.
I noticed that if I move the selector to 4 ohms impedance the noise stops. It might help this?
Also, if I remove the tube V1 12AY7 the noise stops, but obviously the amp does not work...

[stratele52]

lso, if I remove the tube V1 12AY7 the noise stops, but obviously the amp does not work...

Check all the wiring going to this tube. Or any wire act like an antenna close to this tube . 12AY circuit or tube may doing noise

[vincenzo]

lso, if I remove the tube V1 12AY7 the noise stops, but obviously the amp does not work...

Check all the wiring going to this tube. Or any wire act like an antenna close to this tube . 12AY circuit or tube may doing noise

I have to hit the wires that go to the tube with a wooden stick?
How do I know what is the wire that makes noise?

I do not know if my reasoning is logical or wrong, but because the noise exists only acting on the volume pot means that the problem is upstream of the pot? Then, in the preamp section of V1?

One more thing. What do you mean "Are shorting input jacks are working , go to ground ?"

[kagliostro]

Ciao Vincenzo

"Are shorting input jacks are working , go to ground ?"

Ti sta chiedendo se quando non c'è inserito nulla il contatto delle prese jack mette correttamente a massa

l'ingresso evitando che ci sia segnale (disturbo) da amplificare sulle griglie di V1

K

[vincenzo]

Ciao Vincenzo

"Are shorting input jacks are working , go to ground ?"

Ti sta chiedendo se quando non c'è inserito nulla il contatto delle prese jack mette correttamente a massa

l'ingresso evitando che ci sia segnale (disturbo) da amplificare sulle griglie di V1

K

Ok, grazie!! Controllerò anche questo.

[stratele52]

 
I do not know if my reasoning is logical or wrong, but because the noise exists only acting on the volume pot means that the problem is upstream of the pot? Then, in the preamp section of V1?

 

Noise is coming before V2, from input jack to V2.

Shorting jack ; when no guitar plug in a jack , positive of this jack is going to ground . If no , few inches of wire (inside the amp ) act like antenna and d make noise.

When you plug your guitar in a jack , the ground is disconnected from the positive (of the jack )  to receive sound from your guitar .
The other unused jack are kept on ground to be quiet.

Some jack don't have a shorting contact like guitar output jack.

Look for  wrong jack or a wrong wiring .

[vincenzo]

Ok, I checked the input jacks and are shorted to ground. Also, I beat all the wires with a wooden stick and I have not noticed any difference.
Then I proceeded to shorten all the wires and pipes, of the pot and the transformer.
Something has changed. Increasing the normal volume you only hear a pleasant
breath, increasing the volume shiny feels a little more breath.
I noticed that if I increase the presence breath changes, I think it's normal. Also, if I act on the tones you hear the tone change on the breath.
So I thought it was all right. Instead, when I plugged the jack of the guitar the breath becomes hum, noise, like the one that was there before.
It 's normal?
Then I would like to understand how the selection of the output impedance because I noticed that by setting the selector 4, 8, 16 ohms, the output power changes.
Also you could give me some suggestions to fix all the ground wires?

[stratele52]

Ok, I checked the input jacks and are shorted to ground. Also, I beat all the wires with a wooden stick and I have not noticed any difference.

THIS DO NOT MEAN YOU DON'T HAVE ANY PROBLEM


So I thought it was all right. Instead, when I plugged the jack of the guitar the breath becomes hum, noise, like the one that was there before.
It 's normal?

....."PLUG THE JACK OF THE GUITAR...."  ????  YOU MEAN YOU PLUG THE GUITAR IN THE AMP ?

 YES AND NO !  WHAT IS YOUR GUITAR ? SINGLE COILS ?  MANY ELECTRONICAL APPLIANCES IN YOUR ROOM CAN MAKE NOISE WITH YOUR GUITAR PICKUPS ; CELL PHONE , NEON LIGHT , HALOGENE LIGHT , PC COMPUTOR , ELECTRICAL MOTOR. ALL MUST BE SWITCH OFF.

Then I would like to understand how the selection of the output impedance because I noticed that by setting the selector 4, 8, 16 ohms, the output power changes.
Also you could give me some suggestions to fix all the ground wires?

YOU PUT SELECTION TO MATCH WITH YOUR SPEAKER , SAME AS YOUR SPEAKER IMPEDANCE.

You do some good work , be patient  . Congrat.

[vincenzo]

Ok, I checked the input jacks and are shorted to ground. Also, I beat all the wires with a wooden stick and I have not noticed any difference.

THIS DO NOT MEAN YOU DON'T HAVE ANY PROBLEM What should I do?


So I thought it was all right. Instead, when I plugged the jack of the guitar the breath becomes hum, noise, like the one that was there before.
It 's normal?

....."PLUG THE JACK OF THE GUITAR...."  ????  YOU MEAN YOU PLUG THE GUITAR IN THE AMP ? Oh, my bad english.. Yes, I mean plug the guitar in the amp. Attention!! Even without guitar, but only plug the jack!!

 YES AND NO !  WHAT IS YOUR GUITAR ? SINGLE COILS ?  MANY ELECTRONICAL APPLIANCES IN YOUR ROOM CAN MAKE NOISE WITH YOUR GUITAR PICKUPS ; CELL PHONE , NEON LIGHT , HALOGENE LIGHT , PC COMPUTOR , ELECTRICAL MOTOR. ALL MUST BE SWITCH OFF. Everything was turned off except the welder

Then I would like to understand how the selection of the output impedance because I noticed that by setting the selector 4, 8, 16 ohms, the output power changes.
Also you could give me some suggestions to fix all the ground wires?

YOU PUT SELECTION TO MATCH WITH YOUR SPEAKER , SAME AS YOUR SPEAKER IMPEDANCE.

You do some good work , be patient  . Congrat.

[vincenzo]

[stratele52]

..."PLUG THE JACK OF THE GUITAR...."  ????  YOU MEAN YOU PLUG THE GUITAR IN THE AMP ? Oh, my bad english..  Yes, I mean plug the guitar in the amp. Attention!! Even without guitar, but only plug the jack!!

You should hear my italian 

My english is bad too , I' m french Canadian .  I do not criticize you but I wanted to make sure I understand.

Only a guitar cord without any guitar act like antenna , you always have noise .

[vincenzo]

You should hear my italian 

My english is bad too , I' m french Canadian .  I do not criticize you but I wanted to make sure I understand.

Only a guitar cord without any guitar act like antenna , you always have noise .

But I had no doubt! I did not think you criticizing me!

However, if I'm wrong to write the fault is not mine but the Google translator...

For example, above I could not make you understand. The noise is when I plug the guitar and when I plug only the jack.
Should I be worried?

[stratele52]

The noise is when I plug the guitar and when I plug only the jack.
Should I be worried?

One problem at time . No guitar no noise , is not the amp  . Noise with guitar plugged ; check the guitar

You use Google translate ? I use often that is not bad 

[vincenzo]

Ok, I will check the guitar. But already your answer makes me happy!
But, tell me a'' else. Is it normal that the breath changes by adjusting the tone controls?
And by acting on the presence control? And because the breath is weaker in the bright channel?

I promise you that when you come to Sicily you will be my guest for dinner!

[silverfox]

Vincenzo,

I do  not say this is a problem. I have a question about one of the images in your pictures above. I hope some one will answer for me. Please do not get distracted from what you are doing by this general question for everyone to offer answers.

In post 30 above, image #2, I noticed several transformer leads grounded by lug to the chassis.

I've seen this technique in old radios. Is this a good practice? Why won't this cause noise? My take would be, these leads are not neutral?? Are they center taps? That would work.

Silverfox.

[griehund]

Just finished building this same amp.  No hum anywhere.  I don't know what I can add to the conversation but wondering if you're using a multi-tap output transformer.

[stratele52]

But, tell me a'' else. Is it normal that the breath changes by adjusting the tone controls?
And by acting on the presence control?

_YES

And because the breath is weaker in the bright channel? 

I DO NOT KNOW FOR NWO

I promise you that when you come to Sicily you will be my guest for dinner!

Yeah Sicily !!  What  a dream

[vincenzo]

Just finished building this same amp.  No hum anywhere.  I don't know what I can add to the conversation but wondering if you're using a multi-tap output transformer.

Yes, my transformer have a different wire to ground.

http://www.hammondmfg.com/pdf/EDB290DEX.pdf

[vincenzo]

But, tell me a'' else. Is it normal that the breath changes by adjusting the tone controls?
And by acting on the presence control?

_YES

And because the breath is weaker in the bright channel? 

I DO NOT KNOW FOR NWO What it means (NWO)?

I promise you that when you come to Sicily you will be my guest for dinner!

Yeah Sicily !!  What  a dream

[stratele52]

Sorry Vincenzo ,

NWO   

 I may write NOW 

[vincenzo]

The other day, due to a faulty capacitor, had a voltage to the grid of a tube power of +40 V instead of - 40 V. Consequently, the tube went into incandescence.
Now, I noticed that this tube, when high volume sound, it emits flashes of blue and began to crackle.
It 'possible that you will be spoiled when it became incandescent?

[kagliostro]

Easily that tube is DEAD

K

[vincenzo]

Easily that tube is DEAD

K

As I imagined!! In fact I've already proceeded to order a pair of 6L6GC.

[griehund]

Just finished building this same amp.  No hum anywhere.  I don't know what I can add to the conversation but wondering if you're using a multi-tap output transformer.

Yes, my transformer have a different wire to ground.

http://www.hammondmfg.com/pdf/EDB290DEX.pdf

Sorry for the confusion.  The picture you posted looks like your power transformer.  If your output tranny is multi-tap (4,8,16 olms) and the unused taps are not trimmed short and/or twisted together they could be a source of humming.  Enjoy your build.

[stratele52]

Sorry for the confusion.  The picture you posted looks like your power transformer.  If your output tranny is multi-tap (4,8,16 olms) and the unused taps are not trimmed short and/or twisted together they could be a source of humming.  Enjoy your build.

Are you sure of that ?  Many output power transformers use multi-tap with a selector (  Marshall and other)  with no problem . I built some myself.

I desagree with your statement.

[griehund]

Sorry for the confusion.  The picture you posted looks like your power transformer.  If your output tranny is multi-tap (4,8,16 olms) and the unused taps are not trimmed short and/or twisted together they could be a source of humming.  Enjoy your build.

Are you sure of that ?  Many output power transformers use multi-tap with a selector (  Marshall and other)  with no problem . I built some myself.

I desagree with your statement.

I'm positively sure about dying and paying taxes.  Other than that not so much.  Just repeating the warnings I receive as a novice.   

[stratele52]

  Other than that not so much.  Just repeating the warnings I receive as a novice.   

I do not want to criticize but do not take any truth to what is written on the web and especially not repeat this without nuance.

Vincenzo never happen to repair the amplifier in this way

[vincenzo]

Hi,

do not worry, I'm not gone...
I'm waiting for the speaker, and, in the meantime, I'm dedicated to the build of the cabinet.

I made Alder cabinet painted with shellac and wax. Very beautiful. I will show pictures soon!

I also want to show you a video to make you feel the amp, so you can judge if it is okay or not. But I do not know how to post it in the forum. Could someone help me?

Now I have a question. In the attached image, you can see the diode in series with the plate and a .01 cap between 4 and 6 pins. Assuming that the 680V voltage from the PT is to be applied to 4 and 6 pins, the diodes have the safety function. Now, I've noticed that the voltage at 4 and 6 pins and ground is not 340V but 125V. That is, my tester to measure a fraction of a second 340V and then the reading is stable on 125V 
Obviously, if I measure between 3 or 5 pin and ground il read 340V. From wath I measure the amp should not work, instead it works.
Then I do not understand the function of the cap.

[sluckey]

I also want to show you a video to make you feel the amp, so you can judge if it is okay or not. But I do not know how to post it in the forum.

Don't try to post the actual video file here. Instead, upload the video to youtube. Then simply post a 'link' to the video in this forum.

I've noticed that the voltage at 4 and 6 pins and ground is not 340V but 125V. That is, my tester to measure a fraction of a second 340V and then the reading is stable on 125V

The voltage at pins 4 and 6 is no longer AC. Only the positive half cycles of the AC waveform pass thru the diodes, so what you have is pulses of DC. Your meter does not know how to measure those pulses. This is OK. Nothing to be concerned about.

I do not understand the function of the cap.

SS diodes switch on and off abruptly and this switching action can generate fast noise spikes. The cap should reduce or eliminate these noise spikes.